Ford F series Owner's Manual page 255

NOTE: Confirm by observation that the front
driveshaft is not rotating prior to
towing with the rear wheels off the
ground.
Place transfer case in N (Neutral).
NOTE: The transfer case neutral setting is
located between 4H and 4L. In order to
place the transfer case in neutral, first
place the lever in the 4H position, then
push down (toward the ground) on the
shift knob and at the same time pull
slightly rearward until the lever is
between the 4H and 4L position. With
the ignition in the on position, both
4x4 and LOW RANGE indicator lights
will be off when the transfer case is in
neutral. These lights will also be off
when the transfer case is in the 2H
position.
There are no wrecker or recreational vehicle
towing restrictions on method or distance if the
above preparations are made.
Vehicle speed should not exceed 55 mph
(88 km/h). This applies with the front wheels
off the ground, the rear wheels off the
ground, or both front and rear wheels on the
ground.
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